A. Field of the Invention
The present invention relates generally to the field of subscriber station apparatus and, more particularly, to new and improved station apparatus which is provided with two or more handsets and a common signalling unit. The handsets and the signalling unit are selectively operable for multiline operation in a conference arrangement or independently of each other and on any of the telephone lines connected to the apparatus.
B. Description of the Prior Art
Many arrangements have been proposed by the prior art for selective operation of a telephone set in a multiline telephone system wherein the telephone set is equipped with various buttons or switching arrangements for selecting operation on a particular one of the multiple lines. Such multiline telephone sets are sometimes referred to as key telephone systems and commonly provide a button corresponding to each telephone line and a hold button. Such arrangements are described in U.S. Pat. Nos. 2,936,341 which issued to L. J. Greshel et al. on May 10, 1916; 2,769,035 which issued to L. W. Droel on Oct. 30, 1956; and 2,589,180 which issued to F. E. Wood et al. on Mar. 11, 1952.
Other arrangements of the prior art have utilized additional receivers or earphone portions with conventional telephone sets operating on a single telephone line. Arrangements of this type for long distance use and for people who are hard of hearing are shown in U.S. Pat. Nos. 1,239,702 which issued to R. Lagus on Sept. 11, 1917 and 923,603 which issued to W. H. Taylor on June 1, 1909.
Another arrangement utilizes two microphones connected into a single telephone line so that either or both microphones may be utilized to transmit on the single telephone line. An arrangement of this type is shown in U.S. Pat. No. 2,308,014 which issued to R. Lee on Jan. 12, 1943.
Telephone system arrangements of the prior art have also provided various conference systems wherein a number of subscribers are all connected to a common line. A control arrangement for a conference system is shown in U.S. Pat. No. 3,470,322 which issued to C. F. Rice et al. on Sept. 30. 1969 and includes a controlling telephone set which is switchable between the various subscriber lines to bring subscribers into a conference arrangement by making successive calls on the appropriate lines.
While the above-described arrangements of the prior art are generally suitable for their intended use, these arrangements all utilize conventional telephone apparatus with some additional elements or pushbuttons to operate on multiple line systems or in conference arrangements. However, these prior art arrangements do not provide for the independent usage by one or more subscribers of a telephone arrangement utilizing common signalling apparatus which is selectively operable on one line or a multiple number of lines. Further, none of the arrangements provide telephone apparatus with a common signalling unit and in a common housing which may be utilized for the purpose of selective multiline operation and conference arrangements desirable in many applications and locations such as in offices and in homes.